Retinal Blood Flow Measurement Using Multi-Beam Doppler OCT
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Solution Overview
Problem
Current methods for measuring retinal blood flow are limited by their inability to accurately determine blood flow rates in all directions due to high-frequency background Doppler interference, which affects the accuracy of vessel blood flow measurements near the optic disc.
Innovation Solution
An apparatus and method that utilize a light source, light splitting module, reference arm module, sample arm module, and control system, where the central line of the probe light extends through the rotation axis of the scanning unit, allowing for accurate measurement of blood flow by eliminating high-frequency background Doppler through controlled optical-path shifting and phase shift signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single-beam Doppler OCT is used to measure blood flow, then the measurement is simple and quick, but the blood flow information in directions perpendicular to the probe beam cannot be obtained, making it impossible to obtain actual blood flow rate
Solution Approach 1:
The patent divides the measurement task into multiple directional components by using multi-beam illumination. Instead of relying on a single beam, multiple beams are directed at the vessel from different angles to capture blood flow information in multiple directions, which is then synthesized to obtain the actual blood flow rate vector.
Solution Approach 2:
The patent transitions from one-dimensional measurement (single beam along one direction) to three-dimensional measurement (multiple beams from different spatial angles). By introducing angular dimensions through multi-beam configuration, the system can resolve blood flow vectors in multiple directions and calculate the true blood flow rate.
2Measurement precision
If three-dimensional scanning of retina is performed to obtain vessel directions and calculate Doppler angle, then actual blood flow rate can be calculated, but the measurement is less accurate when vessels are perpendicular to probe beam and cannot measure blood flow in all retinal areas
Solution Approach 1:
The patent creates a measurement system that is universally applicable to vessels in any orientation and location within the retina. By using multiple beams that can be directed at different angles, the system can measure blood flow in vessels whether they are parallel, perpendicular, or at any intermediate angle to the probe beam, making it suitable for all retinal areas including the optic disc.
3Measurement precision
If multi-beam and multi-angle probe light is used to obtain actual blood flow rate, then measurement accuracy improves, but the system becomes complex with two Michelson interferometers that are difficult to adjust and have lower sensitivity due to reduced power of each probe light
Solution Approach 1:
The patent merges multiple measurement functions into a single interferometer system. Instead of using two separate Michelson interferometers, the invention combines multi-beam illumination with a single interferometer, where the interferometer processes signals from multiple beams simultaneously. This reduces system complexity while maintaining the ability to measure blood flow in multiple directions.
Solution Approach 2:
The single interferometer is designed to handle multiple functions: it processes interference signals from multiple probe beams incident at different angles, enabling it to measure blood flow velocity vectors in multiple directions. This multi-functional design eliminates the need for multiple interferometers while preserving measurement capabilities.
4Measurement precision
If fundus vessels are scanned near the optic disc, then blood flow in this critical area can be measured, but high-frequency background Doppler interference occurs that affects measurement accuracy
Solution Approach 1:
The patent extracts and separates the harmful high-frequency background Doppler signals from the useful blood flow measurement signals. By using multi-beam illumination with specific angular configurations, the system can identify and isolate the background interference components, then remove them through signal processing to obtain clean blood flow measurements in the optic disc region.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables precise measurement of blood flow rates in both single and multiple vessels near the optic disc by avoiding high-frequency background Doppler interference, thereby improving the accuracy and reducing errors in retinal blood flow assessment.
Implementation Method 1
OCT can provide tissue structures with high resolution and high sensitivity by measuring a depth-related scattering light
Implementation Method 2
the OCT technology can also be used to detect Doppler shift of the scattering light to obtain motion information of a fluid and sample
Implementation Method 3
the reference light and the probe light interfere with each other to generate interference light
Data Source
AI summary
An apparatus and a method for measuring blood flow of vessels are provided. The apparatus includes a light source, a light splitting module, a reference arm module, a sample arm module, a probing module, and a control system. The sample arm module includes a scanning unit and an optical-path shifting device. A probe light is obtained from the light splitting module, and a central line of a main light of the probe light extends through a rotation axis of the scanning unit. The probe light is reflected by the scanning unit to the optical-path shifting device. When the optical-path shifting device is rotated between a first position and a second position respectively, the probe light scans a vessel in fundus to obtain a first phase shift signal and a second phase shift signal blood flow rates and total blood flow of all the vessels near an optic disc are determined.